Radium surface

Benes P (1990) Radium in (continental) surface water. In The environmental behavior of radium. Vol. 1. Inti Atomic Energy Agency, Vienna, p373-418... 

Radon is a naturally occurring, chemically inert, radioactive gas. It is colorless, odorless, and tasteless. It is part of the uranium-238 decay series, the direct decay product of radium-226. Radon moves to the earth s surface through tiny openings and cracks in soil and rocks. High concentrations of radon can be found in soils derived from uranium-bearing rocks, such as pitchblende and some... 

As shown in Table I, radium content of surface soils not associated with U mining or milling varies by slightly more than an... 

Data on surface radium concentrations has been compiled for 394 of the 474 quadrangles covering the conterminous 48 states. The resulting distribution is illustrated in Figure 2, where the parameters shown for the distribution are calculated from the binned data. This distribution has a GM of 25 Bq kg and geometric standard deviation (GSD) of 1.75. Based on this distribution, approximately 20% of the surface radium concentration data are above 40 Bq kg and 0.7% are above 100 Bq kg... 

While these data and the resulting maps are useful in illustrating both the trends and variability in surface radium concentrations, detailed field examination of surface radium concentrations in selected areas is needed to determine the reliability of... 

Figure 2. Distribution of the surface radium concentration data from the National Airborne Radiometric Reconnaissance survey for 394 1° by 2° quadrangles covering most of the contiguous 48 states. The distribution parameters are calculated from the data and the lognormal distribution based on the geometric mean., and standard deviation from the data is shown as a solid curve.

Figure 3. Distribution of surface radium concentrations for a quadrangle (a) with a GM < 20 Bq kg and for a quadrangle (b) with a GM > 40 Bq kg. The curves represent lognormal distributions based on the distribution parameters calculated from the data.

As noted in Table I, average surface radium concentrations appear to vary by about a factor of 20. This can also be seen from the distributions from the NARR data. Soil permeabilities, on the other hand, have much larger variations, and thus, in principle, may have a greater influence on the spatial variations in average indoor radon concentrations that have been observed. As with the case of surface radium concentrations, the spatial variability of air permeabilities of soils is an important element in developing a predictive capability. 

Factors influencing the production and migration of radon in soils have been examined, and various sources of geographic data have been discussed. Two significant soil characteristics include air permeability and, less importantly, radium concentration. While there are, at present, few opportunities to compare the larger-scale data with on-site field measurements, those comparisons that have been made for both surface radium concentrations and air permeability of soils show a reasonable correspondence. Further comparisons between the aerial radiometric data and surface measurements are needed. Additional work and experience with SCS information on soils will improve the confidence in the permeability estimates, as will comparisons between the estimated permeabilities and actual air permeability measurements performed in the field. 

Radon s source is a step in the transmutation of several elements uranium —> thorium — radium —> radon —> polonium —> lead. (There are a number of intermediate decay products and steps involved in this process.) Radon-222 forms and collects just a few inches below the surface of the ground and is often found in trapped pockets of air. It escapes through porous soils and crevices. 

Source. Uranium-238 is present in small amounts in most rocks and soil. Uranium has a half-life of 4.5 billion years. It decays to other elements such as radium, which breaks down to radon. Some of the radon moves to the soil surface and enters the air, whereas some remains below the soil surface and enters the groundwater. 

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